I think this is a very personal decision based on what your goals are and what your body works best with. Working out fasted can be very beneficial for fat loss.
Personally, when I work out early am, I don't eat. When I had a personal trainer he thought it might be beneficial for me to eat before working out. We tried real food, protein shakes and protein bars and pretty much everything made me nauseous. I don't work out well with food of any kind in my stomach. It makes me feel sloshy and gross. I do think it helped me with my weight loss, but really, I wouldn't have been able to change it anyway.
When I work out in the afternoon, I also need to be careful not to have eaten anything for up to an hour before. My body just doesn't like food in it if I'm going to be moving a lot.
Every body is different and I can only say that for me, I trained fasted my whole life but no longer do that.
I work out 4-5 days a week and on my lifting/CrossFit days, up at 6am, I have a banana with a little almond butter and sea salt with a huge glass of coconut water. When I stopped fasting and went this route my performance improved greatly, no flagging with energy and strong until the end. On the days that I do Bikram I'll have a whey shake about 3 hours beforehand and remain strong in that damn 100 degree room for the 90 minute session.
My reason? Well.. I'm on a gaining path to get big and strong to go with my lean and mean.
It depends on how early I think. I get up at 5:30 a.m. to workout regularly and there's just no time which is fine with me. Working out fasted has some real benefits to it and I suggest reading everything you can here about it and intermittent fasting. Working out without food in my stomach also makes me feel lighter and less bogged down with digestive issues.
Low carb pre-workout options. 3 Answers